Hi Steve,

On 13.12.23 01:15, Steven Rostedt wrote:

On Wed, 13 Dec 2023 00:04:45 +0000
Alexander Graf [off-list ref] wrote:

quoted

With KHO (Kexec HandOver), we want to preserve trace buffers across
kexec. To carry over their state between kernels, the kernel needs a
common handle for them that exists on both sides. As handle we introduce
names for ring buffers. In a follow-up patch, the kernel can then use
these names to recover buffer contents for specific ring buffers.

Is there a way to use the trace_array name instead?

The trace_array is the structure that represents each tracing instance. And
it already has a name field. And if you can get the associated ring buffer
from that too.

struct trace_array *tr;

         tr->array_buffer.buffer

         tr->name

When you do: mkdir /sys/kernel/tracing/instance/foo

You create a new trace_array instance where tr->name = "foo" and allocates
the buffer for it as well.

The name in the ring buffer is pretty much just a copy of the trace 
array name. I use it to reconstruct which buffer we're actually 
referring to inside __ring_buffer_alloc().

I'm all ears for alternative suggestions. I suppose we could pass tr as 
argument to ring_buffer_alloc() instead of the name?


Alex




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